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Cumic Plus - Converting to Electric

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Old 01-12-2015, 09:20 AM
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hrtully
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Default Cumic Plus - Converting to Electric

I have owned and flown a few Cumic Plus sailplanes 117". Loved the way they flew. I have one hanging in the rafters in great condition. Ive been out of the hobby for a few years and wanting back in. I am considering converting this to electric . My questions are: Has anyone done this model or a very close equal and if so what was procedure. From my search the planes flying weight is about 65-70 oz. I do own an eflite outrunner 400 740kv motor with the lipos, ESC etc. Is this capable of launching this plane. Last question, do these old planes have much of a value, I dont want to hack it if its a really desired plane as is. If anyone can advise it would greatly be appreciated, Thanks so much
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Old 01-16-2015, 08:39 PM
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I can't comment on the value of the plane.

What kind of climb rate are you expecting? I would recommend you plan for between 70 and 100 watts/pound for sport flying and about 130 watts/pound if you will be entering contests.

So let's call it 4.5 pounds all up once you convert to electric. You would want a motor that puts out between 300 and 450 watts. I have no idea of the specs for your e-flite motor. Would need to know the max recommended amps and max recommended voltage. A link would help.

how hard is the conversion? That depends on how the plane is set-up. You will hack off the nose and put in a firewall/motor mount. Is there room for the motor in the nose?

Where will you put the battery?

how much lead and wood will you be removing, in terms of weight, to put the motor in?

Where are the servos?

That's it for starters.


Photos would be helpful.
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Old 01-16-2015, 09:34 PM
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aeajr, Thank you for your reply. My main concern was wattage size of motor. Since posting this, I found an article on converting a Bird Of Time which is close to same size and weight of Cumic plus. I made the assumption that an eflite outrunner 400 indicated 400 watts, way off on that one. You confirmed everything that the Bird Of Time conversion indicated and I appreciate you sharing your knowledge. I can work out the mechanics, weight and balance issues by now knowing motor info. Thanks again and have a great day (and some warm weather)
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Old 01-17-2015, 06:20 AM
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A popular motor series for doing e-glider converstions is the Turnigy Gliderdrive. This is essentially an outrunner inside a can so you don't have to worry about anything hitting the spinning housing. In addition it has the wire connections on the back to you don't have an issue running the wires in such a way that they will be hit by the spinning can.

Take a look:
http://www.hobbyking.com/hobbyking/s...20&currentPage=

I think the 3850 960kV would be perfect with a 10X6 or 11X5 prop on 4S Should give a good climb. Use a 40 amp or larger ESC.
A more powerful set-up would be the 3858 - 4.6 840kv on a 14X6 on a 4S pack Use a 50 amp or larger ESC Might go vertical.
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Old 01-17-2015, 08:01 AM
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Hi
I have just fitted a Turnigy Gliderdrive 3850-960kv motor to my Hi Fly glider using my existing prop 12.5x10 which produces about 280 watts at 27amps with a 3 series lipo. This prop is the only one of this approx size that I have, but it is far too big. I will change it shortly for a 12x6 prop. My glider weighs 42 oz (just over 21/2 lbs) so I am getting about 100 watts/lb. If you use a 4series lipo on yours with a 10/6 0r 11x7 prop as aeajr states above, it should give 500 watts up to 35 amps max. I am using a Turnigy Sentry 40amp ESC, which is good for a short burst to 50 amps. Waiting for good weather to see how it goes. This motor is a very nice piece of work. The motor has no external cables. It has three male connections for the ESC cables at the rear of the casing instead. This makes it easier to set up. I made three 7" extensions to connect to the ESC. You will require 3mm screws to fit it to the front motor nose block. Have fun.
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Old 01-17-2015, 10:11 AM
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Thanks to both of you for the great info. I was surprised at how much the price has dropped on motors and accessories compared to 7 years ago. I live in rural Ohio surrounded in bean and corn fields on a few acres. I have enough room to launch and land with electric set up but not enough room to set up spool wench. Just looking for a comfortable climb out so I can step outside an have some fun this summer. Going to order suggested items and see where it leads. If I get hung up in the process I may drop back in for some help. Thanks aeajr and franciscan, Have a great day
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Old 01-17-2015, 12:29 PM
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Turn this into a build thread. Post photos of your work and what you did. I guarantee someone will find it helpful. And I would enjoy following along.
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Old 01-17-2015, 01:36 PM
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Just to give you some ideas on starting. I had to cut off my nose section just behind the original 3/8" thick front motor mount. My fuselage is square tapering to a circle at the motor mount.The original power was a brushed 600 motor and cells. I needed at least 38mm dia space for the new motor. I found an epoxy bottle(5 min) which was 40 mm diameter and just right to form a ply tube. I made the tube using 1/64th ply sheet and wound two/three layers around the bottle using white glue. The tube was about 3" long. After it was set I made a new 6mm thick motor mount ring and drilled the required mounting holes and air holes. In hindsight I do not think I needed the air holes as the motor run should not be very long and heat should not be a problem. The ring diameter was just right to provide a force fit into the tube . I glued the ring into the tube and checked the motor fit and when all was dry I glued the tube into the fuselage ensuring that the original down thrust (aprox 5deg) was maintained. I have no idea what a Cumic Plus looks like and you may have to do something different to my mods but they may help in you defining your method. I would enjoy your build thread if you decide to go that route.
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Old 01-17-2015, 02:54 PM
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Thanks again for info, every details helps. When I get to work on this I will photo document details and post. Looking forward to getting started. Thanks Again
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